1. Field of the Invention
The present invention relates to an etching apparatus and, more particularly, the present invention relates to a wet etching apparatus including a substrate mask.
2. Description of Related Art
In general, Flat Panel Displays (FPDs) may be classified into Liquid Crystal Displays (LCDs), Field Emission Displays (FEDs), Organic Light Emitting Diode (OLED) displays, and so forth.
The fabrication of an FPD typically includes a cleaning process, a deposition process, a photolithographic process, and an etching process. The etching process is absolutely necessary to form fine patterns according to a design specification. The etching process may be largely divided into a dry etching process and a wet etching process.
The dry etching process is an anisotropic etching process for selectively etching a thin layer formed on a substrate using a plasma. The dry etching process may be classified into a reactive dry etching process, which is performed by plasma-discharging a reactive gas under a predetermined pressure to cause a chemical reaction, and an ion dry etching process, which is performed by colliding generated ions.
The wet etching process is an isotropic etching process using an etchant. When compared with the dry etching process, the wet etching process is appropriate for mass production of large-area devices because better selectivity and etching uniformity and effective cost reduction can be obtained.
The wet etching process may be performed using a dip method or a spray method. In the dip method, a substrate having a thin layer is completely dipped in an etchant. In the spray method, an etchant is sprayed on the surface of a thin layer formed on a substrate using an additional spray unit. The dip method can obtain a uniform etch rate, while the spray method can obtain a good etching profile.
The spray method is described in detail as follows.
Initially, a substrate is loaded into an etching chamber using a transfer roller.
Thereafter, an etchant is supplied using a pump from a chemical tank to a piping unit. The chemical tank is positioned outside the etching chamber to store an etchant.
The piping unit is connected to a plurality of nozzles to spray the etchant on the substrate. Thus, the wet etching process can be performed by spraying the etchant on the substrate via the nozzles.
However, in the spray method, since the etchant is sprayed via the nozzles under a constant pressure, the etchant may collide with the underlying substrate to generate microbubbles.
As a result, a thin layer formed on the substrate cannot be etched uniformly, and a defective pattern may be obtained.